The present invention relates generally to devices for producing linear movement.
Helical coil electromagnetic launchers, also known as coil guns, are efficient devices for generating linear forces that can be used to accelerate macroscopic particles to a high velocity, or convey particles for various uses, such as aerospace, automotive, farming, earth-moving equipment, conveyance devices such as elevators or conveyors, or any industry or type of device where linear motion is needed or desired. Linear accelerators such as helical coil launchers can be used to move particles quickly and with a significant amount of force. The efficiency of the helical coil launcher increases as the scale of the launcher increases, making the launcher a particularly useful device in principle for linear acceleration of relatively large objects.
One reason that the helical coil launcher is such an effective linear force generator is that it has a large inductance gradient between an armature coil/projectile and a stator coil, which can be two or more orders of magnitude greater than that of a conventional rail launcher. Therefore, in comparison to the rail launcher, the helical coil launcher can generate the same accelerating force at much lower currents.
However, to optimize the potential of the helical coil launcher in practice, the turns of the stator coil must be efficiently commutated.
The present invention provides an apparatus for efficient commutation of stator coil turns for a helical coil electromagnetic launcher. An annular brush assembly is disclosed having an annular support and a plurality of electrical contacts, such as brushes, disposed circumferentially about the annular support for contacting the stator coil. The electrical contacts are connected to one another in parallel.
The annular brush assembly of the present invention allows multiple, simultaneous contacts about the stator coil, so that transition between turns of the stator coil is effectively negated as the annular brush assembly, connected to an armature coil, moves axially along the stator coil. With an absence of transition effects between stator coil turns, the commutation energy is correspondingly minimized. There is accordingly less resistance to linear movement of the armature coil between turns, and significantly less arcing, which results in less wear on the electrical contacts and more efficient operation of the helical coil launcher.
The plurality of contacts may be disposed about the annular support substantially symmetrically. The contacts may extend radially outwardly from the annular support radially inwardly, or through the annular support. The annular support may be a separate piece, or may be an integrated portion of a body assembly connected to the armature coil, and may include a number of apertures for holding the plurality of contacts. A biasing means may be provided for biasing the contacts towards the stator coil.
The present invention also provides a projectile for a helical coil launcher including an armature coil, a body assembly connected to the armature coil, and an annular brush assembly, the annular brush assembly including a plurality of electrical contacts, such as brushes, extending circumferentially about the annular brush assembly for contacting a first end of a portion of the stator coil slidingly engaged with the projectile. The plurality of electrical contacts are connected to one another in parallel.
Preferably, the projectile includes a rail brush for contacting a conductive rail, the rail brush being electrically coupled to the electrical contacts of the annular brush assembly, preferably via an end contact. Most preferably, the projectile further includes a second annular brush assembly, the second annular brush assembly being configured for contacting a second end of the portion of the stator coil.